We propose to investigate the use of drugs and biological molecules tagged with aminopolycarboxylate chelating groups as radiopharmaceuticals for the localization of tumors in vivo. These chelating agents should form highly stable complexes with approximately 50 metallic elements. The anti-tumor antibiotic bleomycin will be chemically modified in several ways to yield semisynthetic products containing powerful metal chelating groups; other drugs, such as rifamycin and daunomycin, will be similarly treated. The proteins transferrin, fibrinogen, and albumin will also be conjugated with chelating agents. The products will be purified and characterized by appropriate physical, chemical and biochemical techniques to detect changes in conformation or biological activity. Studies of organ distribution, tumor uptake, metabolism, toxicity, pyrogenicity, and immunogenicity will be carried out as necessary, using appropriate animal models. The subcellular distribution of radiolabel in tumors will also be investigated. Techniques will be optimized for rapid, specific, and quantitative labeling of the products by mixing with radioactive metal ions such as 111 indium, 99m technetium, or 67 gallium in suitable buffer solutions. This separation of synthetic organic chemistry from radiochemistry simplifies the preparation and use of radiopharmaceuticals.